I once was really struggling in an AP History Class and had to cram for the class final. I did well on the final and the AP test the next week, but got a C in the class.

My biology teacher told me he'd raise my c+ to an a if I got a five on the AP. I did. He recanted and said he assumed that was impossible. Still very slightly annoyed about it 18 years later.

I don't think high school grades always reflect how much you actually learned.